JP4773886B2 - U packing and fluid pressure single acting cylinder - Google Patents

Description

  The present invention includes a U-packing that is fitted over a seal groove of a piston of a fluid pressure single-acting cylinder and that maintains fluid tightness between a bottom side and a rod side partitioned by the piston, and a fluid pressure unit including the U-packing. Related to dynamic cylinders.

  Among fluid pressure cylinders using hydraulic pressure, water pressure, or the like, there is a fluid pressure single acting cylinder that generates a linear driving force by supplying a working fluid only to the bottom side of the piston. In this fluid pressure single-acting cylinder, U packing is used to maintain fluid tightness between the two so that the working fluid does not leak from the bottom side where the working fluid should act to the opposite rod side.

  An example of a fluid pressure single acting cylinder using such a U-packing will be described below with reference to FIG. FIG. 4 is a cross-sectional view illustrating a fluid pressure single-acting cylinder using a U-packing, which is the background art of the present invention, and is described in Patent Document 1.

  The fluid pressure single-acting cylinder 30 includes a cylinder body 25, a piston 26 that slides fluid-tightly in the cylinder body 25, and a piston 26 that is provided at the tip, and outputs a linear driving force generated by the working fluid to the outside. And a piston rod 27.

  A seal groove 26a is provided on the outer periphery of the piston 26, and a U-packing 23 is installed in the seal groove 26a to maintain fluid tightness between the bottom side fluid chamber Ca and the rod side fluid chamber Cb partitioned by the piston 26. Has been.

  The bottom side of the cylinder body 25 is closed by a cylinder head 25a, and a passage 25c for the flow of working fluid is provided in the cylinder head 25a. The rod side of the cylinder body 25 is closed by a cylinder head 25b that projects the piston rod 26 in a fluid-tight and slidable manner.

  The fluid pressure single-acting cylinder 30 receives supply of working fluid to the bottom side fluid chamber Ca during driving, pushes the piston 26 upward in this figure, and when not driven (refers to the case where the piston 26 is lowered). The piston 26 is lowered by being pushed by the load on the piston rod 27.

  At this time, the U-packing 23 prevents the working fluid from leaking from the bottom side fluid chamber Ca to the rod side fluid chamber Cb, but the leakage cannot be completely prevented. The working fluid accumulated in the fluid chamber Cb prevents the piston 26 from reaching its upper limit.

  Therefore, the fluid pressure single acting cylinder 30 includes a check mechanism 28 for returning the working fluid accumulated in the rod side fluid chamber Cb to the bottom side fluid chamber Ca when the piston 26 tries to reach the upper limit. ing.

  The check mechanism 28 includes fluid passages 28a, 28b provided between the piston 26 and the piston rod 27 so as to communicate with the bottom side fluid chamber Ca from the rod side fluid chamber Cb on the rod side of the U packing 23. 28c and a check valve 28d provided at the outlet of the fluid passage 28c to the bottom side fluid chamber Ca.

  When the pressure of the working fluid in the rod side fluid chamber Cb becomes higher than the pressure of the working fluid in the bottom side fluid chamber Ca, the check valve 28d allows the working fluid to flow from the rod side fluid chamber Cb to the bottom side fluid chamber Ca. Distribution is permitted.

  Thus, in the fluid pressure single acting cylinder 30 provided with the check mechanism 28, when the piston 26 is about to reach its upper limit, the pressure of the working fluid in the rod side fluid chamber Cb is changed to the working fluid in the bottom side fluid chamber Ca. When it becomes higher, the working fluid in the rod-side fluid chamber Cb is returned to the bottom-side fluid chamber Ca, and the piston 26 can reach the upper limit without hindrance.

  However, such a check mechanism 28 requires the check valve 28d, and it is necessary to provide the fluid passages 28a, 28b, and 28c in the piston 26 and the piston rod 27, which is expensive.

  As a method for solving this problem, a U-packing mainly having a sealing function may be provided with a check function, and techniques such as Patent Documents 2 to 5 have been proposed so far.

However, none of the methods can be applied in a harsh environment such as the balance condition of a very high pressure working fluid between the rod side fluid chamber Cb and the bottom side fluid chamber Ca as in the present invention.
Japanese Patent Laying-Open No. 2003-49806 (FIG. 1) Japanese Patent Publication No.49-49330 (FIGS. 2 and 3) Japanese Utility Model Publication No. 59-51232 (FIGS. 2, 3, and 4) Japanese Utility Model Publication No. 6-51658 (FIG. 1) JP-A-8-35504 (FIGS. 1 and 2)

  The present invention is intended to improve the above problem, and is a harsh environment in which fluid tightness is maintained between a bottom side and a rod side which are fitted in a seal groove of a piston of a fluid pressure single acting cylinder and partitioned by the piston. An object of the present invention is to provide a U-packing that can perform a check function below, and a fluid pressure single-acting cylinder using the U-packing.

The U-packing of the present invention is a U-packing that is fitted in a seal groove of a piston of a fluid pressure single-acting cylinder and maintains fluid tightness between a bottom side and a rod side partitioned by the piston,
The opening side of the U-packing is used as the bottom side, a return hole is provided to communicate the opening side and the non-opening side, and the working fluid pressure on the bottom side (hereinafter referred to as “positive pressure”). Is greater than the working fluid pressure on the rod side (hereinafter referred to as “back pressure”), the return hole is closed at the rod side wall of the seal groove, while the back pressure is greater than the positive pressure. In this case, the U-packing is configured to move in the seal groove so that the return hole is opened with respect to the rod side wall .
The return hole is formed by a rigid return hole forming body that is embedded only in a necessary portion in the U packing when the U packing is molded .

  Moreover, the fluid pressure single acting cylinder of the present invention is characterized by using the U packing.

  The U-packing of the present invention is provided with a return hole in the U-packing that is fitted in the seal groove of the piston of the fluid pressure single-acting cylinder and maintains fluid tightness between the bottom side and the rod side partitioned by the piston. However, since the check function is exhibited by moving in the seal groove and opening and closing the return hole, the check function can be exhibited even in this harsh environment.

  Moreover, since the fluid pressure single acting cylinder of the present invention uses the U packing, the effect of the U packing is exhibited as a cylinder.

  Hereinafter, embodiments (examples) of the present invention will be described with reference to the drawings.

  1A and 1B show an example of a U-packing according to the present invention. FIG. 1A is a front view thereof, FIG. 1B is a cross-sectional view thereof, and FIG. 1C is a main part of a fluid pressure single-acting cylinder using the U-packing. Sectional drawing, (d) is an enlarged view of the U-packing portion of (c), and (e) is an enlarged view of the state where the U-packing has moved to the bottom side as compared with (d).

  The U packing 3 shown in FIGS. 1 (a) and 1 (b) has a ring shape as a whole, and a cross section cut along a plane passing through the center thereof is substantially U-shaped, and its opening side is in a natural state. The ring-shaped U packing 3 has a shape in which the outer lip portion 3a and the inner lip portion 3b expand in the outer diameter direction and the inner diameter direction, and a return hole 1 is provided to communicate the opening side with the non-opening side. It is characterized by that.

  A portion forming a space between the outer lip portion 3a and the inner lip portion 3b is referred to as an opening portion 3c, and the return hole 1 communicates the non-opening side of the U packing 3 with the opening portion 3c on the opening side. I am letting.

  The return hole 1 is provided at a position that equally divides the circumference of the non-opening side. Specifically, the rubber molding of the U-packing 3 is performed at a necessary portion for forming and maintaining the return hole 1. Sometimes, it is formed by a rigid return hole forming body 1a that is appropriately embedded so as not to appear on its surface.

  Here, the necessary part means that the return hole 1 is maintained even if the return hole forming body 1a is deformed when the U-packing 3 is used under high pressure. The vicinity of the position where the return hole 1 is provided.

  In this example, the return hole forming body 1a has a rectangular parallelepiped shape, and the return hole 1 passes through the center portions of the two opposing surfaces.

  A fluid ditch 3d that allows the working fluid in the return hole 1 and the opening 3c to flow to the outer peripheral side of the U-packing 3 is formed at a required place on the axial end edge of the outer lip 3a.

  The material of the U-packing 3 is the same material as the normal U-packing, functionally in a natural state, and is shaped to fit into the inner and outer diameters of the groove into which it fits. The outer lip 3a expands and contracts to such an extent that it can be expanded from the outer diameter of the groove, and the outer lip portion 3a sufficiently has an inner circumference of the cylinder against the positive pressure (referred to as the pressure of the working fluid acting on the opening side). The surface and the inner lip 3b are in fluid-tight contact with the bottom peripheral surface of the groove to exhibit a sealing function, specifically, polyurethane (PU. TPU, PUR, which is a rubber-based synthetic resin). ), Nitrile rubber (NBR), thermoplastic elastomer (TPE) and the like are suitable.

  This U packing 3 is used for a fluid pressure single acting cylinder 30 as shown in FIG. This fluid pressure single-acting cylinder 10 is used for raising and lowering a fork of a forklift, and includes a cylinder body 5, a piston 6 that fluidly slides within the cylinder body 5, and the piston 6 at one end. The end protrudes out of the cylinder body 5 and includes a piston rod 7 that gives a linear drive to an external load.

  Both sides of the cylinder body 5 are sealed with cylinder heads. In FIG. 1C, the bottom cylinder head 5a is visible. The cylinder head 5a is provided with a passage 5c for flowing a working fluid.

  A seal groove 6a is provided on the outer periphery of the piston 6, and the U-packing 3 of the present invention is inserted into the seal groove 6a so that the opening side is the bottom side (bottom side fluid chamber Ca side). The fluid tightness between the bottom side fluid chamber Ca and the rod side fluid chamber Cb partitioned by the piston 6 is maintained.

  The basic functions of the cylinder body 5, piston 6, piston rod 7 and the like are the same as those of the fluid pressure single acting cylinder 30 described in FIG.

  There is a predetermined gap between the seal groove 6a and the U-packing 3 in the axial direction of the piston 6, that is, in the sliding direction, due to a pressure difference between the working fluid in the bottom side fluid chamber Ca and the working fluid in the rod side fluid chamber Cb. The U-packing 3 provided with the return hole 1 moves in the axial direction within the seal groove 6a and exhibits a check function. Hereinafter, a description will be given with reference to FIGS.

  FIG. 1D shows a state in which the pressure (positive pressure) of the working fluid in the bottom side fluid chamber Ca is the pressure of the working fluid in the rod side fluid chamber Cb in the state before driving and before the piston 6 reaches the upper limit. It is higher than (back pressure), and due to this pressure difference, the end surface on the non-opening side of the U packing 3 is in contact with the rod side wall surface 6b of the seal groove 6a, and the return hole 1 is closed by the rod side wall surface 6b.

  In this state, the U packing 3 exhibits a fluid tight function between the bottom side fluid chamber Ca and the rod side fluid chamber Cb, and the working fluid does not flow from the bottom side fluid chamber Ca to the rod side fluid chamber Cb. .

  FIG. 1 (e) shows a state in which the working fluid leaking into the rod-side fluid chamber Cb gradually decreases in the state where the piston 6 further rises from FIG. 1 (d) to reach its upper limit. It shows a state in which the pressure (back pressure) is contained in the fluid chamber Cb and is higher than the pressure (positive pressure) of the working fluid in the bottom side fluid chamber Ca.

  At this time, due to the pressure difference, the opening side end surface of the U packing 3 abuts against the bottom side wall surface 6c of the seal groove 6a, while the non-opening side end surface is separated from the rod side wall surface 6b and the return hole 1 is opened. It becomes a state.

  Therefore, in this case, the working fluid in the rod-side fluid chamber Cb is returned to the bottom-side fluid chamber Ca through the return hole 1, the opening 3c, and the fluid concave groove 3d of the U-packing 3, and the piston 6 has no problem. , It can rise to its upper limit.

  That is, the U-packing 3 provided with the return hole 1 according to the present invention has a simple configuration in which only the return hole 1 is provided, and can perform a necessary check function. In addition, FIG. Therefore, the check mechanism 28 that is indispensable in the fluid pressure single-acting cylinder 30 becomes unnecessary, and the cost can be reduced.

  In other words, the U-packing 3 of the present invention is externally fitted in the seal groove 6a of the piston 6 of the fluid pressure single-acting cylinder 10, and is fluid-tight between the bottom side (Ca) and the rod side (Cb) partitioned by the piston 6. It is possible to perform a thorough check function in the harsh environment of maintaining

  Moreover, the fluid pressure single acting cylinder 10 using the U packing 3 can exhibit the effect of the U packing 3 as the cylinder 10.

  Further, in the U-packing 3 of the present invention, the return hole 1 for performing the check function is formed and secured by the rigid return hole forming body 1a, so that the rod side fluid chamber Cb and the bottom side fluid chamber Ca are provided. The return hole 1 can be more reliably secured even under a harsh environment such as the contact condition of a very high-pressure working fluid between them and the check function can be reliably exhibited.

  Moreover, the fluid pressure single acting cylinder 10 using the U packing 3 can exhibit the effect of the U packing 3 as the cylinder 10.

  FIG. 2 shows another example of the U-packing of the present invention, where (a) is a front view thereof, (b) is a cross-sectional view thereof, and (c) is an essential part of a fluid pressure single-acting cylinder using the U-packing. FIG. Accordingly, the same parts as those already described are denoted by the same reference numerals and redundant description is omitted.

  The U packing 3A is different from the U packing 3 of FIG. 1 in that a backup ring 4 is fitted on the outer periphery of the non-opening side.

  Further, the return hole forming body 1b is not a rectangular parallelepiped shape as shown in FIG. However, if the return hole forming body can secure the return hole 1 and is a rigid body that does not deform even under high pressure, it is necessary and sufficient, and it does not depend on its outer shape. It is the same.

  The backup ring 4 is a bias cut type, and the U-packing 3A is first fitted into the seal groove 6a of the piston 6 without the backup ring 4, and thereafter, on the outer non-opening side of the U-packing 3A. It is fitted in combination.

  The backup ring 4 is formed of a hard material and prevents the U packing 3A from being deformed under high pressure so that the sealing function of the U packing 3A can be better exhibited. Further, the deformation preventing function has a positive effect on securing the return hole 1 under high pressure.

  Therefore, according to this U packing 3A, in addition to the basic function of the U packing 3, the sealing function and the check function can be more fully exhibited.

FIG. 2 (c) shows a fluid pressure single acting cylinder 10A using the U packing 3A.
This fluid pressure single acting cylinder 10A can exhibit the effect of the U packing 3A as a cylinder.

  FIG. 3 shows another example of the U-packing of the present invention. (A) is a front view thereof, (b) is a cross-sectional view thereof, and (c) is an essential part of a fluid pressure single-acting cylinder using the U-packing. FIG.

  The U-packing 3B is made of the same material as the U-packing 3 of FIG. 1 in common with the U-packing 3 of FIG. 1, but the non-opening side is made of a harder material. The difference is that the hard part 3e is manufactured and is integrally molded as a whole.

  The main part of the return hole 1 is formed in the hard part 3e to maintain the shape under high pressure and secure the return hole 1.

  Further, since the hard portion 3e is hard and cannot be expanded and attached, the seal groove 6a 'of the piston 6 has a detachable ring body 6d at its rod side wall portion. At the time of mounting 3B, a procedure is required in which the ring body 6d is once removed, the U packing 3B is fitted, and then the ring body 6d is returned to its original state.

  According to such a U-packing 3B, the hard portion 3e is provided, and the return hole 1 is formed therein. Therefore, in addition to the same effect as the U-packing 3 in FIG. 1, the backup ring 4 in FIG. 2 is provided. Similar to the U packing 3A, it also exhibits a backup ring effect.

  FIG. 3C shows a fluid pressure single acting cylinder 10B using the U packing 3A. The fluid pressure single acting cylinder 10B can exhibit the effect of the U packing 3B as a cylinder.

  Further, the U-packing and fluid pressure single-acting cylinder of the present invention are not limited to the above-described embodiments, and various modifications and combinations are possible within the scope described in the claims and the scope of the embodiments. .

  The U-packing of the present invention is fitted on the seal groove of the piston of the fluid pressure single-acting cylinder, and exhibits a check function in a harsh environment where the fluid tightness between the bottom side and the rod side partitioned by the piston is maintained. It can be used in all industrial fields that are required.

An example of the U packing of this invention is shown, (a) is the front view, (b) is the sectional view, (c) is principal part sectional drawing of the fluid pressure single acting cylinder using the U packing, ( d) is an enlarged view of the U-packing portion of (c), and (e) is an enlarged view of the state where the U-packing has moved to the bottom side compared to (d). The other examples of U packing of the present invention are shown, (a) is the front view, (b) is the sectional view, (c) is the principal section sectional view of the fluid pressure single acting cylinder using the U packing. The other examples of U packing of the present invention are shown, (a) is the front view, (b) is the sectional view, (c) is the principal section sectional view of the fluid pressure single acting cylinder using the U packing. Sectional drawing which illustrates the fluid pressure single acting cylinder using U packing which is background art

Explanation of symbols

1 Return hole
1a, 1b Return hole forming body
3-3B U packing
5 Cylinder body
6 Piston
6a Seal groove
6b Rod side wall
7 Piston rod
8 Check mechanism
10-10B Fluid pressure single acting cylinder

Claims (2)

A U-packing that is fitted in a seal groove of a piston of a fluid pressure single-acting cylinder and maintains fluid tightness between a bottom side and a rod side partitioned by the piston,
The opening side of the U-packing is used as the bottom side, a return hole is provided to communicate the opening side and the non-opening side, and the working fluid pressure on the bottom side (hereinafter referred to as “positive pressure”). Is greater than the working fluid pressure on the rod side (hereinafter referred to as “back pressure”), the return hole is closed at the rod side wall of the seal groove, while the back pressure is greater than the positive pressure. In this case, the U-packing is configured to move in the seal groove so that the return hole is opened with respect to the rod side wall .
The U-packing is characterized in that the return hole is formed by a rigid return-hole forming body that is embedded only in a necessary portion in the U-packing when the U-packing is formed . A fluid pressure single acting cylinder using the U packing according to claim 1.

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